Electric motor with external rotor

Abstract

An electric motor comprises a stator fixedly mounted to a shaft and a rotor, surrounding the stator, rotatably mounted to the shaft. The shaft is stiffened by a plurality of plates mounted to the shaft and held thereon under significant compression by a lock nut. The compression is high enough to inhibit bending that would otherwise occur from external forces acting on the shaft. The plates also form the windings for the motor.

1. In an electric motor of the type comprising an internal stator, including a shaft fixedly mounted to a structural support and having multiple windings capable of reversible current flow to alter the winding polarity, and an external rotor rotatably mounted to the shaft and having multiple magnets radially spaced about the periphery of the stator, with each of the magnets having at least one predetermined pole; the improvement wherein:
 the stator comprises a plurality of plates on the shaft under compression in a range of approximately 6×10 4  and 10×10 4  Newtons to sufficiently inhibit bending of the shaft due to external forces that would otherwise tend to cause the windings to contact the magnets.  
 
   
   
     2. The electric motor according to  claim 1 , wherein the plurality of plates forms a winding core that carries the multiple windings. 
   
   
     3. The electric motor according to  claim 2 , wherein the plates form winding poles with caps on the end of each pole to retain the windings on the winding poles. 
   
   
     4. The electric motor according to  claim 1 , wherein the plates are held in the compression range by at least one lock nut. 
   
   
     5. The electric motor according to  claim 4  wherein the locknut is threaded onto the shaft. 
   
   
     6. The electric motor according to  claim 4  wherein the length of windings is less than about 20 inches. 
   
   
     7. The electric motor according to  claim 6  wherein the plurality of plates comprises approximately 980 plates. 
   
   
     8. The electric motor according to  claim 4  wherein the ratio of the length of the windings to the diameter of the external rotor is approximately 5:1. 
   
   
     9. The electric motor according to  claim 1 , wherein the plurality of plates form winding poles that define a winding axis, oriented such that the winding axis is not parallel to the shaft longitudinal axis. 
   
   
     10. The electric motor according to  claim 9 , wherein the winding axis is at an angle of at least 10 degrees relative to the shaft longitudinal axis. 
   
   
     11. The electric motor according to  claim 9  wherein the length of windings is less than about 20 inches. 
   
   
     12. The electric motor according to  claim 11  wherein the plurality of plates comprises approximately 980 plates. 
   
   
     13. The electric motor according to  claim 1  wherein the shaft has an annular shoulder and the plurality of plates is compressed between a locknut and the annular shoulder. 
   
   
     14. The electric motor according to  claim 13  wherein the locknut is threaded onto the shaft. 
   
   
     15. The electric motor according to  claim 13  wherein the length of windings is less than about 20 inches. 
   
   
     16. The electric motor according to  claim 15  wherein the plurality of plates comprises approximately 980 plates. 
   
   
     17. The electric motor according to  claim 13  wherein the ratio of the length of the windings to the diameter of the external rotor is approximately 5:1. 
   
   
     18. The electric motor according to  claim 1  wherein the spacing between the magnets and periphery of the stator is approximately 1 mm or less. 
   
   
     19. The electric motor according to  claim 18  wherein the magnets are neodymium. 
   
   
     20. The electric motor according to  claim 1  wherein the magnets are neodymium. 
   
   
     21. The electric motor according to  claim 1  wherein the length of windings is less than about 20 inches. 
   
   
     22. The electric motor according to  claim 21  wherein the plurality of plates comprises approximately 980 plates. 
   
   
     23. The electric motor according to  claim 21  wherein the ratio of the length of the windings to the diameter of the external rotor is approximately 5:1. 
   
   
     24. The electric motor according to  claim 1  wherein the plurality of plates comprises approximately 980 plates. 
   
   
     25. The electric motor according to  claim 1  wherein the ratio of the length of the windings to the diameter of the external rotor is approximately 5:1.